Remove `user_interacted_projects` table

Investigate if user_interacted_projects is used in any place.

It looks like we should remove this table #360823 (comment 1600117812), but we should double-check we are not using the data in any feature.

Given the history of this table / model in gitlab-foss!17327 (merged), there should be no feature that uses this.

Grepping around for the following keywords reveals only a tiny amount of code to only populate the table from the events table.

• user_interacted
• UserInteractedProject
• project_interaction

Implementation Guide

• Check if Data WarehouseImpact Check team if they use it.
• Remove associated code - completed with !137791 (merged)
  • What does the code do? Are we removing any functionality that we are not aware of?
  • Can we remove the table after understanding the code?
• Drop the table in milestone 16.8 or later. Docs.